In urban environments trees have a hard time surviving. Much of this is due to the abuse we inflict on them. Even when a tree well is provided, and a grate on top is installed to permit air flow and water flow while preventing the soil from being compacted.
Most new tree grates in Ottawa look like the above picture. It does work, but in a limited way. The City long ago came up with a standard that the minimum opening for a tree to survive in was approx. 4’x4′.
Naturally, this minimum opening became the maximum opening.
Look at this picture of what another City does to help its trees not just survive, but flourish:
Note that the Boston grate has two additional sections that can be added to the tree grate. They triple the air, water, and uncompressed growing media root zone.
Not every tree installation has room for a larger grate. But over the years, I have had too many battles with city engineers or street planners or transitway installers over this issue. Some of these fine City employees cannot get their head around the difference between a minimum standard and a maximum. To them, minimum is truly the “one size fits all” rule.
I had others argue that larger openings are dangerous to pedestrians because they aren’t perfectly smooth with the concrete sidewalk, especially after years of wear and tear and frost heave. And others have argued that it’s simply too expensive to supply a larger grate or install more cobbles on the surface. They’d rather come back more often to replace the dead tree.
Or maybe they just really wish those damn trees would go away and let them get along with real important stuff, like traffic signal ducts.
But it is worth knowing that other cities do better, and we can demand our city improve too, once we know about better practices.